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Prasad July'ze, 193s I MACHINE TOOL Benjamin P. Graves, Cranston. andArthur F.

Bennett, West Barrington, R. I., assignors to As sociated Patents, Inc.,a corporation of Ohio Application March 9, 1934, Serial No. 714,808

34Claims.

The present invention relates to improvements in machine tools, and morespecifically to a class of machines which include a movable supportmounted von ways to impart relative feeding and return movements to thework and operating tools.

The invention is herein disclosed as embodied in a milling machine whichcomprises a rotary milling cutter and a movable work support driven lofrom a reversible electric motor through connections which includecooperating feed screw and nut driving elements and slow feed and quicktraverse clutch connections. A It is one object of the present inventionto provide in a machine of this general descriptioma novel and improvedtake-up device having a yielding take-up action to maintain a tightworking engagement between the feed screw and nut elements which isparticularly well adapted to insure the accurate positioning of thetable at all times under varying strains during its travel in eitherdirection without at the same time causing excessive frictional Wear orbinding of.the parts.

It is another object of the invention to provide a novel and improvedfluid pressure control system for the machine for controlling theoperation of the several cooperating devices including particularly theslow feed and quick traverse clutch and the take-up device to ease of!the take-up strain between the Afeed screw and nut elements during amanual or quick traverse operation of the table.

It is another object' of the present invention to provide novel andimproved means controlled by the direction of operation of the drivingconnections for the table and rendered operative upon reversal of thedirecton of drive with the simultaneous shift of the clutch to quicktraverse o position to delay the operation of theclutch until after thereversal has actually taken place.

With these and other objects in view, as may hereinafter appear, onefeature of the present invention consists in the provision in .the tabledrive of a novel and improved take-up device for maintaining a tightoperating engagement between the feed screw and nut elements to insurean accurate and even movement of the table regardless of the f orceexerted on the table in either direction by the operation of the cutter.This device comprises a second nut screw threaded to the feed screw andsupported in fixed anguiar relationship to the usual feed nut, and atake-up member yieldingly actuated and having a cam action of relativelylarge advantage for effecting a relative axial movement of the nuts tomaintain a tight operating engagement between the feed screw and nutelements. With this construction and arrangement of the parts, asubstantially irreversible cam action is provided so that the strainexerted on the table in either directionl by the engagement of therotating cutter with the work is taken up against a rigid assembly ofthe two nuts which is positively supported against endwise movement ineither di- 10 rection on the machine frame.

In accordance with certain features of the present invention, a uidpressure control system is provided which comprises a uidfpressureoperated piston for moving the slow feed and quick 15' traverse clutchto quick traverse position, a second fluid pressure operated piston formoving the take-up member to ease oiI the take-up device,

a main control valve for supplying uid under pressure simultaneously toeach of these pistons, '20 and a manual feed control valve arrangedduring the' manual operation of the table to supply fluid pressure ltothe piston for easing off thek take-up device. 'I'he main valve -may becontrolled manually or automatically during the op- 25 eration of thetable by means of electrical connections including an electromagnet ashereinafter more fully to be described. In accordance with anotherfeature of the invention, a reversible fluid pressure pump is pro- 30videddriven from the reversible motor which is arranged upon reversal ofthe table drive with a simultaneous shift of the clutch from/slow feedto quick traverse position to delay the operation K of the clutch untilreversal lhas actually taken 35 place.

The several features of the invention consist also in the devices.combinations and arrangement of parts hereinafter described and claimed,y which together with the advantages to be attained thereby will bereadily understood by one skilled in the art from the followingdescription taken in connection with the accompanying drawings, in whichFig. 1 is a view in front elevation of a manufacturing type of millingmachine embodying the vseveral features of the invention; Fig. 2 is adetail sectional view in front elevation illustrating particularly thedriving connections for the table; Fig. 3 is a detail sectional view onan enlarged scale of a portion' of Fig. 2, illus- 50 tratingparticularly the take-up mechanism for the feed screw and nut drivingconnections; Fig.

4 isy a sectional view taken on the .line 4 4 of Fig. 3; Fig. 5 is adetail sectional view taken substantially on the line 5-5 of Fig. 2 toillustrate 55 particularly the hand feed connections for driving thetable; Fig. 6 is a detail sectional view taken on the line 6--6 of Fig.5; Fig. 7 is a detail sectional View taken on the line l-'l' of Fig. 5;Fig. 8 is a view similar to Fig. 7 showing the hand feed control memberpositioned to engage the hand feed; Fig. 9 is a detail sectional viewtaken on the line 9 9 of Fig. 2 to illustrate particularly a part of thedriving connections from the motor to the table; Fig. 10 is a detailsectional view taken on the line |0-l0 of Fig. 2 to illustrateparticularly the control valve and solenoid for controlling theoperation of the slow feed andA quick traverse clutch; Fig. 11 is adetail view in front elevation of the reversible lubricating oil pumpfor the machine; Fig. 12 is a sectional view taken on the line |2-I2 ofFig. 11; Fig. 13 is a view similar to Fig. 12 illustrating' theoperation of the pump in a reverse direction; Fig. 14 is a sectionalview taken on the line |4|4 of Fig. 11; Figs. 15 and 16 illustrate adifferent embodiment of certain features of the invention, and moreparticularly of the take-up mechanism as applied to a milling machineprovided with a stationary feed screw and rotating feed nuts, Fig. 15being a detail sectional view in front elevation of the feed screw androtating nut elements and take-up device applied thereto, and Fig. 16being a sectional view taken on the line |6|6 of Fig. 15; Figs. 17 to 19inclusive, are somewhat diagrammatic views of the oil pressure controlmechanism for controlling the operation of the slow feed and quicktraverse clutch and the backlash take-up device for the feed screw andnut elements of the table drive, Fig. 17 showing the parts in positionfor the power feed operation, Fig. 18 showing the parts in position forquick traverse operation, and Fig. 19 showing the parts in position forhand feed operation; Fig. 20 is a diagrammatic view of the electricalconnections for controlling the several cooperating mechanisms of themachine; and Fig. 21 is an explanatory diagrammatic view of theelectrical connections illustrated in Fig. 20.

The machine illustrated in the drawings as embodying in a preferred formthe'several features of the lpresent invention, comprises amanufacturing type milling machine in which the work is vsupported on awork support Aor table moveable in a horizontal plane with relation to avertically adjustable rotary milling cutter. The table is power drivenby means of a reversible two-speed electric motor, and interveningdriving connections which include a rotatable feed screw mounted on thetable, a cooperating stationary nut, a slow traverse gear train, a quicktraverse gear train, and a clutch connection movable from a neutralposition to engage one or the other of said geartrains to drive thetable alternatively at a feeding or quick traverse rate.

Referring more specifically to the drawings, a work supporting table isindicated at 40 mounted to slide on ways 42 formed on the base 44 of themachine. A rotary milling cutter spindle 46 is supported above the tablein a casing 48 which is supported for vertical adjustment on the machinecolumn 50. With the machine herein disclosed, the cutter spindle isdriven by means of a separate motor 52 through connections generallyindicated in dotted lines in Fig. 1.

The work table 40 is driven from a reversible two-speed electric motor56 through direct connections which include slow feed and quick traversegear trains and clutch connections for alternatively connecting one orthe other of these trains to drive the table. As best shown in Figs. 2,5 and 9, there is supported' on the armature shaft 58 of the motor agear 6i! which meshes with a gear 62 secured to a connecting drive shaft64. The shaft 64 is connected to drive the main drive shaft 66 of themachine at a slow traverse rate through gear connections comprisingintermeshing take-ofi gears l0 and l2 secured respectively to the shaft64 and to an idler shaft 14. A second gear 16 on the idler shaft 14meshes with a gear 18 on a shaft 80 which carries a worm 82 adapted tomesh with a worm gear 84 loosely sleeved to turn on the drive shaft 66.The shaft 66 may be driven at a quick traverse rate from the shaft 64through gear connections comprising a gear 86 secured to the shaft 64which is arranged to mesh with a sleeve gear 88 mounted to turn on ashort pivot shaft 90. A bevel gear 92 formed integrally with the sleevegear 88 meshes with a corresponding bevel gear 94 loosely sleeved to 66.

A slow feed and quick traverse clutch member 96 is rigidly secured tothe driving y'shaft 66 between the slow feed worm 84 and the quicktraverse bevel gearl 94, and is provided at one end with a jaw toothedclutch 98 arranged to engage with a corresponding clutch member formedon the face of the worm gear 84, and at its other end is provided with ajaw toothed clutch face I 00 arranged to engage with a corresponding jawtoothed clutch member formed on the adjacent Aface of the bevel gear 94.Movement of the slow feed and quick traverse clutch S6 to engagealternatively Awith the slow feed driving worm gear 84 or with the quicktraverse bevel gear 94 is effected by an endwlse movement of the drivingshaft 66 controlled by means of a shifting 'rod |02 which passes throughan axial bore in the drive shaft 66. A nut |04 and a collar |06 aresecured to the shaft to engage with opposite ends of the drive shaft 66to cause the drive shaft 66 to move f axially with the shifting rod |02,while permitting the drive shaft to rotate with relation thereto. Aheavy compression spring |08 coiled about the shifting rod |02 between abearing plate ||0 secured to the machine frame and the collar |06 on therod |02 tends normally to hold the shaft 66 and clutch 96 to the left asviewed in Figs. 2 and 5 with the clutch face 98 in engagement with theslow feed worm gear 84. Movement of the drive shaft 66 and the clutch 96in an opposite direction to engage the quick traverse bevel gear 94 iseffected by means of a hydraulically operated piston ||2 arranged toslide in a pressure chamber ||4 and secured by means of a connecting rod||6 to move axially with the shifting rod |02 and drive shaft 66.

The table 40 is driven from the drive shaft 66 as illustrated in Figs. 2and 3, through driving connections which comprise a rotatable feed screw|24 supported at each end in bearings in the table, and a stationaryfeed nut |26 which is rigidly supported against rotational or endwlsemovement in the machine frame so that rotational movements of the feedscrew will cause corresponding endwise movements to be imparted to thefeed screw and table 40. For rotating the feed screw |24 there is alsokeyed thereto a driving nut |28 which is externally supported in themachine frame to permit rotational movement thereof by means of rollerbearings |30, and is held against lengthwise movement with relation tothe frame by means of end thrust bearings |32 interposed betweensupporting brackets |33 and adjustable turn on the drive shaft shown inFig. 4, to take up the nuts.

check nuts |34 screw-threaded to each end of the driving nut |28. Forrotating the driving nut |28 and feed screw |24 to impart the requiredfeeding movements to the table 40 from the drive shaft 66, an externalgear |36 formed on the driving nut |28 is arranged to mesh with theidler gear |38 which, in turn meshes with the driving gear |40 on thedrive shaft 66.

In order to secure a tight operating engagement between the feed screw|24 and the stationary nut |26, and thus prevent any possible backlashor chatter in the table drive, there is provided with the presentconstruction an additional nut |42 which is screw-threaded to the feedscrew |24 and is keyed against rotation therewith on the machine frame.'I'he nut |42 is moved axially with relation to the feed screw and tothe xed nut |26 by means of a take-up nut |44 provided with internalleft and right screw threads which mesh with correspondingly threadedportions of the stationary nut |26 and additional nut |42. The angularposition of. the take-up nut |44 to tighten or loosen the nut 42 andfeed screw with relation to the fixed nut |26 is controlled, as bestshown in Figs. 3 and 4, by means of a rack |46 which meshes with acorresponding gear segment |48 formed on the take-up nut |44. Acompression spring |50 coiled about the rack rod |46 and seated at oneend in a recess formed in the bearing |52 for the rack rod, and at itsother end against a collar |53 on the end of the rack rod, tends to movethe rack to the left, as 'I'he collar |63 is held in position by anadjustable nut |54 to permit an adjustment of the take-up tensionexerted by the spring acting through the take-up nut |44. It willreadily be seen that the take-up connections described are arranged topermit a relatively heavy take-up tensioning strain to,be exerted on thenuts |26 and |42 through the agency of a relatively light springtension. This arrangement has the further advantage that the action ofthe take-up nut |44 is irreversible, the threads'of the take-up nutbeing disposed at a less than critical locking angle, so that, the heavystrains imparted to the table by the action of the milling cutter on theWork are -not transmitted to the spring 50, but are entirely taken upagainst the fixed nut |26 rigidly mounted on the machine frame, so thata positive control of the position of the table is maintained. under allcon-L ditions during feeding movements of the table in either direction.For rotating the take-up nut |44 in an opposite direction to loosen theoperating connection between the nuts and the feed screw |24, a piston|56 is secured to the right-hand end of the rack bar |46, as shown inFig. 4, and is arranged to slide in an oil pressure cylinder |58, f

so that the introduction of oil under pressure through the inlet pipeillustrated at |59 in Fig. 4, will move the piston and rack bar totheright against the pressure of the spring |50 to loosen the nuts.

A second embodiment of certain features of the take-up device formaintaining a tight operating engagement between the feed screw and nutelements of the table drive as applied to' a stationary feed screw androtating driving nuts, is illustrated in Figs. 15 and 16 of thedrawings. In these figures, a stationary feed screw |60 is employedrigidly secured in the usual manner at opposite ends to the worksupporting table 40, and has mounted thereon two feed nuts |62 and |64which are provided with the external gears |66 and |68 which mesh withthe previously described idler gear |38 of the table drive. The feednuts are externally supported in a bracket |10 formed on the machineframe by means of roller bearings |12, and are supported againstlengthwise movement in the machine by means of end thrust bearings |14and |16 which engage with collars |18 and |80 secured respectively toopposite ends of the two nuts |62 and |64. With this arrangement of thedriving connections, it will readily be seen that a constant angularrelationship is maintained between the two feed nuts |62 and |64 by theengagement of the external gears |66 and |66 with the idler gear |38.

In order to secure a tight operating engagement between the rotatingfeed nuts |62 and |64 and the stationary feed screw |60 and thus toprevent any possible backlash or chatter in the table drive, mechanismis provided for imparting a relative axial movement to the nuts to bringthese elements tightly into engagement with the threads of the feedscrew |60. This mechanism comprises two sleeve members |82 and |84loosely sleeved on the nut |62 and interposed between a bearing formedby the bracket 10 and the end thrust bearing -|14 above described.Corresponding cam surfaces |86 are formed on the adjacent'faces of thesleeve members |82 and |84, so that a relative rotational movement ofthese members will act through the end thrust bearing |14 to move thenut |62 to the left as shown in Fig. 15 to secure a tight operatingengagement between the nuts |62 and |64 and the feed screw |60. 'I'hesleeve member |82 is held against turning by means of a key |88. .n

The angular position of the sleeve |84,With relation to the sleeve |82to tighten or. loosen the nuts |62 and |64 with relation to the feedscrew |60 is controlled as shown in Figs. l5 and 16, by means of a rackwhich may be that designated at |46 inthe iirst embodiment described,and meshes' with a corresponding gear segment |62 formed on the camsleeve |84. The compression spring |50 coiled about the rack rod |46 andseated at one end in a recess formed in the bearing |52 for the rackrod, and at its other end against a collar |53 on the end of the rod,tends to move the rack to the left as shown in Fig. 16 to take up thenuts. The compression spring acts against the cam sleeve to impart alengthwise tensioning strain to the nuts in opposite directions againstthe fixed end thrust bearings. The angle of the cam surfaces employed issuch as to permit the employment of a relatively light strain to securea relatively heavy tensioning strain on the nuts, and is furtherarranged to provide an extremely high resistance to any easing olfactionof the nuts against the combined force of the spring and thefrictional resistance of the cam surfaces. "With this construction'itwill be seen that while a yielding spring pressure is utilized to takeup the nuts, thel arrangement of the cam surfaces |86 provides asubstantially irreversible cam action, so that the entire strain uponthe connections due to the operation of the cutter against the work, istaken up against the end thrust bearings |14 and |16 and the stationarybracket |10 above described, to maintain a positive control of theposition of the table under all conditions during feeding movements ofthe table in either direction. For rotating the cam sleeve |84 in anopposite direction to loosen the operative connection between the nutsand the feed screw |60, a piston which may be the piston |56 of the lrstembodiment of the invention described, is secured to the right hand endof the 4 rack bar |46 as shown in Fig. 16, and is arranged to slide inthe oil pressure cylinder |58, so that the introduction of oil underpressure through the inlet pipe |59 will move the piston and the rackbar to the right as shown in Fig. 16, against the pressure of the spring|50 to loosen the nuts.

The illustrated machine is providedwith hand feed operating connectionstogether with a Vcontrol mechanism therefor which is arranged normallyto maintain the hand feed out of operation, and acts when renderedoperative to permit the engagement of the hand feed and simultaneouslyto move the slow feed and quick traverse c1utch' to neutral position.-The hand feed operating connections as best shown in Figs. 2, 5 and 6,'

comprises a forwardly extending shaft 200 which is mounted for axial androtational movements in a bearing 202. At its forward end the shaft isprovided with a squared end 204 to receive a many ually operable crankhandle of ordinary description, and at its rear end carries a gear 206ar ranged to mesh with a corresponding crown gear 208on the drive shaft66. It will be seen from an inspection of Fig. 5, that the shaft 200 maybe moved rearwardly to bring the gear 206 into operative engagement withthe crown gear 208 only for a lengthwise position of the drive shaft 66which corresponds to a neutral or intermediate vposition of the slowspeed and quick traverse clutch 86. The mechanism for controlling theoperation of the-hand feed comprises a plug 2|0 journalled in a casing2|2 axially in alignment with the drive shaft 66. At its inner end theplug is provided with a bearing surface arranged to engage with the endof the shifting rod |02,

and with an offset cam 2|4 arranged to engage with the face of the gear206 on the inner end of the hand feed shaft 200. For controlling theoperation of the plug 2|0 to impart lengthwise and rotational movementsthereto, a hand lever 2|6 is secured to the side of the plug 2`|0 andextends outwardly through a cam slot 2|8 in the casing 2|2. With theplug in its normal inoperative position, the plug is withdrawn out ofengagement with the shifting rod |02, and the cam 2|4 is positioned toqlock the hand feed shaft 200 and gear 206 in a retracted position outof engagement with the crown gear 208. When it is desired to throw thehand feed into operation, the control lever 2|6 is moved downwardly tothe position shown in Fig. 6 to rotate the plug, and at the same timecause the engagement of the control lever 2 I6 with the cam slot 2|8above described. This movement of the plug acts to move the cam 2|4 topermit a forward movement of the hand feed shaft 200, and simultaneouslymoves the shifting rod |02, drive shaft 66 and clutch 96 to the right,as shown in Fig. 5, against the pressure of the spring |08 to throw theclutch 96 into neutral, and to position the crown gear 208 forengagement with the gear 206 on the hand feed shaft 200.

In accordance with a principal feature of the present invention, acontrol system is provided for controlling the operation of the take-updevice hereinbefore described, to render said device operative toprovide a tight operating engagement between the screw and nut elementsduring the power slow feed of the machine in either direction, andacting simultaneously with the movement of the clutch 96 to quicktraverse position to ease ofi' said device to permit a free workingengagement of the feed screw and nut elements.v There is also providedin the present construction, means rendered operative by the movementsion of the conduit 222 it to be advanced through of the hand feedcontrol member 2|6 into position for engaging the hand feed, to ease offthe take-up device and permit a free operating engagement between thefeed screw and nut elements during the manual operation of the table. Asillustrated in Figs. 17, 18 and 19, an oil pressure control system isprovided for controlling the operation of the slow speed and quicktraverse clutch 86, and also for controlling the operation of thetake-up device. Oil pressure is supplied from a reversible pump 220,directly connected to the armature shaft 58 of the table driving motor56, through a conduit 222 to the inlet |56 to the oil pressure cylinder|58 for controlling the operation of the rack bar |46 of the take-updevice. Fluid under pressure is carried from this point through anextento a valve 224 winch is controlled by the hand feed control lever 2i6, and comprises a channel 225 formed in the plug 2|l, and inlet andoutlet ports 226 and 228 formed in the valve casing. The outlet port 228is connected by a conduit 230 to a'valve 232 which conl its upper endthe piston 234 is connected to the armature 246 of a solenoid 248, andat its lower end is provided with an extension on which is coiled a'compression spring 250 which engages at one end with a collar 252 on theextension, and at its other end with the valve casing 232.

v 'I'he operation of the control system for-slow feed power operation ofthe machine, is illustrated in Fig. 17. As shown in this figure, thehand feed control lever 2I6 is in its inoperative position to permit afree flow of oil under pressure through the valve 224. The solenoid 248is deenergized so that the piston 234 of the valve 232 occupies adepressed position under the influence of its spring 250 to allow apassage for the oil through the outlet 242 to the sump. Under theseconditions no pressure is applied to the pressure cylinder |58 for thetake-up device, so that the rack |46 is permitted to move under thepressure of its spring |50 to secure a tight operating engagementbetween the feed screw and nut elements. Similarly, pressure isexhausted from the cylinder ||4 for controlling the operation of theslow feed and quick traverse clutch 96, so that the clutch is permittedto move to a slow feed position in engagement with the feed worm gear 84under the pressure of the spring |08.

. For a quick traverse operation of the machine,

the solenoid 248 is energized to raise the piston 234, shutting oif theexhaust conduit 242 to the sump. Under these conditions, as illustratedin Fig. 18 of the drawings, the oil pressure is built up in the pressurecylinder |58 to move the rack bar |46 to the right against the pressureof its l spring |50 to relieve the tension of the nuts |26 traversebevel gear 84 to drive the machine at a quick traverse rate.

The operation of the control system for the hand operation of themachine is illustrated in Fig; 19. At this time the solenoid 248 isde-ener- .glzed, allowing the piston 234 to move to its deisconsequently built up in the cylinder |68 to -move the rack bar |46 tothe right against the pressure of its spring |58 to relieve the tensionon the nuts |26 and |42, so that a free operating lengagement isprovided between the feed screw and nut elements to permit an easy andunobstructed operation of the hand feed lever by the operator.

The reversible oil pump 220 in addition to supplying oil under pressureto the uid pressure control system above described, is also arranged tosupply oil for the lubrication of various bearings in the machine, andis further arranged to control the operation of a switch in theelectrical operating connections for the machine including the solenoid248 to delay the shifting of the slow feed and quick traverse clutch toquick traverse posi:- tion when this takes place' upon reversal of thedirection of drive until after reversal has .actualvly taken place. Thepump 220, as illustrated in Figs. 11 to 14 inclusive, is provided withtwo meshing gears 260 and 262 for pumping oil through the connectingpassages of the pump in either direction, the gear 260 being mounted ona drive shaft 264 directly connected to the armature shaft 86 oi' themain driving motor. 'I'he pump is provided with an intake line 266through which oil is drawn through a branch line 266, and ball checkvalve 210 to a chamber 212 adjacent the two gears during a left handoperation oi the table, as illustrated in Fig. 12. or alternatively isdrawn through a branch line 214 and check valve 216 to a chamber 218adjacent the two gears for a right hand operation of the table drive, asillustrated in Fig. 13.

'Ihe pump is also provided with a sliding valve piston 266 which isfitted Within a valve chamber 282 and is journalled to receive a plungeror shaft 264, which carries at its upperv end the switch contact arms266 adapted to close an electric circuit alternatively through switchcontacts 288 for a. left hand drive oi' the table, or through the switchcontacts 296 for a right hand drive of the table. The piston 280 ismounted for a limited sliding movement with relation to the plunger 284between two collars 292 and 294 on the plunger. A compression spring 296coiled about the plunger 284 between two collars 296 and 306 looselysleeved on a reduced portion 302 of the plunger tends at all times toreturn the plunger and switch arms 286 to an intermediate neutralposition.

Assuming that the table is being driven to the left with the gears 260and 262 rotating in the direction of the arrow in Fig. 12, oil is drawnthrough the branch line 268, ball check valve 218 and chamber 212, andis delivered under pressure into the chamber 218 from whence it passesthrough a conduit 304 to the lower portion of the valve chamber 282,forcing the valve piston 280 and plunger 264 upwardly to the positionshown in Fig. 12, closing a circuit through the contacts 288. 'I'hismovement of the valve piston uncovers The control lever 2|6 is l a port886 through which oil now passes under pressure to the inlet line 222 ofthe uid pressure control system above described.

When the main feed motor is reversed to drive the table to the right,the pump gears will be driven in a revrse direction as shown by thearrow in Fig. 13. Oil is now drawn through the branch line 214, ballcheck valve 216 and chamber 218, and is delivered under pressure intothe chamber 212 and the upper portion of the valve chamber 282, causingthe valve piston 260 and plunger 284 to be depressed to the positionshown in Fig. 13 to close the circuit through the switch contacts 280.This movement of the valve piston uncovers a port 306 through which oilnow passes under pressure to the conduit 222 ofthe fluid pressurecontrol system above described.

As the main driving` motor and the gear pump connected thereto come torest upon the stopping or reversal of the table, the spring 296 operatesto centralize the plunger 264 and switch arms 266, thus opening thecorresponding plugging switch contacts 288 or 290. The sliding piston266 is also moved to an intermediate positionclosing both of the ports366 and 606 communicating with the conduit 222 to prevent anyappreciable loss of pressure in the fluid pressure control system atthis time.

For Vthe lubrication oi the various parts of the machine, each oi' thechambers 212 and 218 is connected by means of a small oriilce 8| 6 to alubricating conduit 8|2. 'I'he size of the orifices 3|0 is calculated topermit only a limited flow of oil through the conduit `3|2 which will besuillcient for the proper lubrication of the machine without at the sametime short circuiting the pump. 'Ihese orifices also serve to permit theexhaustion of oil from the chambers 212 and 216, so that the valve'piston 286 can be returned to its neutral or intermediate position underthe pressure oi' the spring 286 without danger of becoming stalled uponthe stopping or reversal of the main driving motor and pump,

In order to maintain the pressure in the fluid pressure control systemat a predetermined value, a relief valve 3|4 is provided in the line 222comprising'a valve head and a stem 3|6 about which is coiled acompression spring 8|8 seated within a cylindrical member 320 which isscrewthreaded for adjustment in the pump casing. Any excess'oil whichescapes through the relief valve `8|4 is carried through an exhaust line322 back to the sump.

In accordance with certain features of the present invention, electricalconnections are provided for controlling the operation of the two speedreversible driving motor and of the iluid pressure control system abovedescribed to secure a simple and efiicient control of these devices forthe power operation of the machine by the operator or automatically bymeans of dogs mounted on the work supporting table. 'Ihe electricalconnections referred to are similar in many respects to those set forthin the application of the present applicant led of even date herewithbut may be brley described as follows in connection with Fig. 1, theelectrical wiring diagram Fig. 20, and the explanatory diagram Fig. 21of the drawings.

The rate and direction of the power operation of the table is controlledby means of a simple arrangement of switch control buttons whichcomprise left and right feed buttons and left and right quick traversebuttons. With the arrangement of the electric connections hereinafter tobe described in connection with the electrical diagram, Fig. 20, therate of travel of the table may be varied to effect either slow feed orquick traverse movement of the table at any point in the table travel ineither direction, or the direction of travel of `the table may bereversed at either a slow feed or quick traverse rate by pressing thedesignated button for establishing the required rate and direction oftravel of the table.w The switch contact buttons for controlling'thedirection and rate of feed of the support are mounted, vas indicated inFig. 1,

in a control post 324 which is located adjacent one side of the table.These buttons are arranged in' two series and comprise four buttons 326mounted in vertical alignment on the table side of the control post tocooperate with corresponding dogs on the table to control the directionand rate of feed of the table, and a second series of manuallycontrolled buttons 328 mounted on the opposite side of the control postto permit the convenient operation of tit controls by hand. Asmore fullypointed out in the copending application of the present applicants abovereferred to, the control post is mounted to turn about a fixed pivot toenable the automatic control buttons 328 to be moved out of the path ofthe dogs when it is desired to manually control the power operation ofthe table. Two additional stop buttons 330 are mounted on a xed portionof themachine frame for engagement with corresponding dogs on the tableto positively limit the movement of the table in either direction. Inorder. to permit an automatic control of the motor speed during thecontinued operation of the table so that the feeding rate may beautomatically adjusted to varying conditions in the making of the cutwithout the necessity of stopping the machine or of shifting clutchconnections under load, a mercury -switch 332 is provided as indicatedin Figures 1 and 20 of the drawings which may be controlled by means ofadjustable table dogs 884 which are mounted for adjustment on the rearside of the table. These dogs are arranged to engage with twocorresponding vertically movable racks 336 and 338 arranged to mesh withopposite sides of a pinion 340 `on a rock Vshaft 842 to which themercury switch is secured.

Referring specifically to the electrical wiring diagram Fig. 20 and theexplanatory diagram Fig. 21, it will be seen that the table drivingmotor 56 and the spindle driving motor 52 are driven from a three phasepower line designated as L1, L and L3. The' table motor is controlled bymeans of a reversing switch having two exciting relays L and R.

'Ihe main switch for the table motor is supported on a panel indicatedin dotted lines at 356 in Fig. 20, and comprises two sets of contactswhich are controlled by the relay coils R and L respectively to connectthe motor and table for right or left hand operation. A high speed andlow speed switch for the table motor 56 is also mounted on the panel350, and cornprises two sets of contacts controlled respectively by therelay coils HS and LS for high speed or low speed operation of the tablemotor.

On another panel indicated at 352 in dotted lines, are carried the mainswitch contacts for the spindle motor 52 controlled by means of tworelay coils SF and SR for opposite directions of rotation of the motorand spindle driven thereby. Y

There are also provided on a panel 354 designated in dot-ted lines inFig. 26, a number of secondary relay switches, which are arranged tocontrol the operation oi the table and spindle switches above describedtogether with the solenoid 248 and valve piston 234 winch 'operate theslow feed and quick traverse clutch 95. These secondary relays comprisethe secondary coils LR and RR controlled respectively by the left andright feed buttons, the coils TL and TR con\ trolled respectively by theleft and right quick traverse buttons, a relay coil RC which controlsthe operation of the slow feed and quick traverse solenoid 248 and valvepiston 234, and also has connections which are arranged under certainoperating conditions to control the operation of the high speed tablemotor and the spindle motor switches.

Two additional secondary relay coils CRR and CRL, also supported on thepanel 254, are provided in the circuit controlled by the plugging switchcontacts 288 and 290, and operate in connection therewith to apply abraking torque for plugging the motor to rest upon stopping or reversingthe drive of the table, and also to delay the operation of the solenoidH2 to shift the clutch to quick traverse 4position upon reversal at aquick traverse rate.

Inasmuch as the several switch relays and the contacting switchescontrolled thereby may be of any well known construction, these partshave been shown conventionally only for simplicity and convenience inillustration.

- Assuming a rest position of the machine and I that it is desired tostart the machine feeding to the left, pressing the Feed left" buttonenergizes the LR coil. LR contacts 4-3 now close tov form a holdingcircuit, LR contacts 2-l3 close, energizing the main contact coil L tostart the table motor, and LR contacts 2-21 also close to energizeeither the SF or SR coil to start the spindle motor. The pressing of theFeed right button with the machine at rest will operate similarly to`start the table feeding to the right. At this point it may be notedthat when the table moves to the left, the plugging switch contactors288 are closed by the operation of the oil pump 220 as above described.so that the plugging switch contactor coil CRL is energized, opening theplugging switch contacts 2-l1 and closing the contacts 2I8. When thedirection of table travel is reversed to the right, the pluggingswitch'contacts 288 are opened, and after the reversal of the electricmotor has actually taken place, the plugging switch contacts 290 closeto energize the CRR coil, causing the plugging switch contacts 2-i6 toopen and the contacts 2-I5 to close.- Y

The connections herein disclosed are particularly adapted for operationupon shifting from a slow feed in one direction to a quick traversemovement of the table in the opposite direction, to delay the shiftingof the clutch to quick traverse position until after reversal hasactually taken place. If it be assumed that the table is feeding to theleft, the pressing of the Fast right" button will operate to reverse themovement of the table at a quick traverse rate as followsz-'I'hecontactors LR, L, LS and SF may be assumed to be closed as well as theplugging switch relay contacts 2-i8 and 2--I8. The pressing of the Fastright button energizes the coil TR. TR contacts lil- Il close,energizing the coil RR. TR contacts I1-28 and 202i close, but the RCcoil is not at this time energized to open the control valve 232 andshift the clutch, because of the fact that the contacts 2-I'l are stillopen. RR contacts 2 4 open, deenergizing LRcoil which opens the maincontactorL. RR contacts il-I also close, forming a holding circuitthrough LR contacts 2--I4 which also close. RR contacts 2-22 energizethe main contactcr coil R, electrically reversing the motor. As themotor and the reversible pump connected thereto stop and start to turnin an opposite direction, the switch arms 286 controlled by the pump arefirst moved to a neutral position t'o disengage the contacts 288 and de-energize the CRL coil, and are then moved to close the contacts 290 toenergize the CRR coil. The CRL contacts 2-I1 are now closed, energizingthe RC coil. The RC contacts 2-3I now close to energize the solenoid248, opening `the main control valve 232 to shift the clutch ferred to.

to quick traverse position.- At the same time RC contacts -8 open todisconnect the spindle circuit, and also to disconnect the low speedcoil I S. RC contact 2-23 also closes to 'energize sthe high speedcontactor HS regardless of the position of the mercury switch abovedescribed. The shift from a slow speed oi' the table to the right to aquick traverse left may be similarly accomplished by pressing the Fastleft button.

For other ways in which the electrical devices may be operated tocontrol theoperation of the machine, reference may be had to thecopending application of the The nature and scope of the invention'having been indicated. and a machine embodying the several features ofthe invention having been specifically described, what is claimed is: y

1. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation to anotherwhich comprises a screw on one of said supports, a pair of nuts threadedto the screw, means for maintaining a constant angular relationshipbetween the nuts, and a take-up device having a take-up action tomaintain a tight operating en- A gagement between said screw and nutelements comprising tensioning means, take-up means actuatedtherebycomprising cam actuating surfaces for imparting relativemovements to the nuts cammed at 'a less than critical locking angl'e toimpart an unyielding relative axial movement to the nuts, and meanscooperating with said take-up device for rigidly positioning said nutson the other of said supports against movement relatively thereto withthe screw in either direction.

2. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation to anotherwhich comprises a screw on one of said supports, a pair of nuts threadedto the screw, means i'or maintaining a constant angular relationshipbetween the nuts. and a take-up device having a take-up action tomaintain a tight operating engagement between said screw and nutelements comprising a spring, a member yieldingly actuated by the springand having cam actuating surfaces cammed at a less than critical lockingangle to imparta relative axial movement to the nuts, and meanscooperating with said take-up device for rigidly positioning said nutson the other oi.' said supports against movement relatively there'-towith the screw in either direction.

3. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation toanpresent applicants above reother which comprises a screw on one ofsaid l means for maintaining a constant angular relationship between thenuts, and a take-updevice having a take-up action to maintain a tightoperating engagement between said screw and nut elements comprising arotatable take-up member supported co-axially with the screw, a springfor rotating said member, cam surfaces rendered operative by therotation of said member and arranged at a less than critical lockingangle to exert an unyieldingrelative take-up strain on the nuts, andmeans cooperating with said take-up member for rigidly positioning saidnuts on the other of said supports against movement relatively theretowith the screw in either direction.

4. A mechanism to. eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation to anotherwhich comprises a screw on one of said supports, a pair of nuts threadedto the screw, means for maintaining a constant angular relationshipbetween the nuts, and a take-up device having a. take-up action tomaintain a tight operating engagement between said screw and nutelements comprising a take-up nut having a left and right screw-threadedengagement respectively with said nuts, said screw threads beingarranged to have an irreversible take-up action, spring means fortensioning the take-up nut, and means cooperating with the take-up nutfor rigidly positioning the nuts on the, other of said supports againstmovement relatively thereto with the screw in either direction.

5. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for ,moving one support with relation to anotherWhiclr comprises a screw on one oi said supports, a pair of nutsthreaded to the screw, means for maintaining a constant angularrelationship between the nuts, and a take-up device having a take-upaction to maintainA a tight operating engagement between said screw andnut elements comprising a take-up nut having a left and rightscrew-threaded engagement respectively `with said nuts, spring means fortensioning the takeup nut, and means cooperating with the take-up nutfor rigidlypositioning the nuts on the other of said supports againstmovement relatively thereto with the screw/in either direction.

6. A mechanism to eliminate backlash between the lscrew and nut elementsof a driving connection for moving one support with relation to another,whiclr comprises a screw on one of said supports, a pair of nutsthreaded to the screw, f

means for maintaining a constant angular relationship between the nuts,positioning means for the n'uts on the other of said supports, and atakeup device having a take-up action to maintain a tight operatingengagement between said screw and nut elements comprising a rotatabletake-up member supported co-axially with the screw, a spring forrotating said member, and cam surfaces rendered operative by therotation of said member to exert a rela-tive take-up strain on the nuts,said cam surfaces beingk disposed to cooperate with said positioningmeans at a locking angle to provide a rigid support against forcesacting on the driven support through said driving connection axially ofthe screw in either direction.

'7. A mechanism to eliminate backlash between relatively movable screwand nut elements of a driving connection for a machine tool supportwhich comprises a feed screw, a pair of nuts locking angle to exert anunyielding axial take-h up strain on one oi said nuts with relation toits bearing, and tensioning means for exerting a take-up tension on saidmember.

8. A mechanism to eliminate backlash betweenrelatively movable screw andnut elements of a driving connection -for a machine tool support whichcomprises a feed screw, a pair of nuts threaded to said feed screw andmeans for relatively rotating said feed screw and nuts including` meansto maintain a constant angular relationship between said nuts, and atake-up mechanism having a take-up action to maintain a tight operatingengagement between said feed screw and nut elements comprising an endthrust bearing engaging each of said nuts to limit axial movement ofeach of said nuts in opposite directions, a take-up member, co-operatingcam surfaces arranged upon movement of said member to move one of saidnuts axially with relation to its end thrust bearing to provide a tightoperating engagement between said feed screw and nut elements, said camsurfaces being cammed at a less than critical locking angle to provide alocking engagement against axial movement of said nuts to actuate saidmember, and tensioning means for exerting a take-up tension on saidmember 9. A mechanism to eliminate backlash between relatively movablescrew and nut elements of a driving connection for a machine toolsupport which 'comprises a non-rotatable feed screw mounted to move withsaid support. a pair of nuts threaded to said feed screw, and means forrotating said nuts including means to maintain a constant angularrelationship between said nuts, a take-up device having a take-up actionto provide a tight operating engagement between said feed screw and nutelements comprising an end thrust bearing for each of said nuts to limitaxial movement of each of said nuts in an opposite direction, a take-upmember, cam surfaces rendered operative by the movement of said memberand cammed at a less than critical locking angle to exert an unyieldingaxial take-up strain on one of said nuts with relation to its bearing,and tensioning means for exerting a take-up tension on said member.

10. A mechanism to eliminate backlash between relatively movable screwand nut elements of a driving connection for a machine tool supportwhich `comprises a rotatable feed screw, a relatively stationary nutthreaded thereto, a second nut threaded to the feed screw keyed againstrotation with relation` to said former nut, and a take-up device forcontrolling the relative axial positions of the nuts to maintain a tightworking engagement between the nuts and the feed screw comprising atake-up nut having a left and right screw thread engagement respectivelywith said nuts, said screw threads being arranged to have anirreversible take-up action, and means for rotating said take-up nut uto impart a relative axial movement to said nuts for securing a tightoperating engagement between the feed screw and nut elements.

11. A mechanism to eliminate backlash between relatively movable screwand nut elements of a driving connection for a machine tool supportwhich comprises a vrotatable feed screw, a relatively stationary nutthreaded thereto, a second nut threaded to the feed. screw keyed lagainst rotation with relation to said former 12. A mechanism toeliminate backlash bei tween the screw and nut elements of a drivingconnection for moving one support with relation to another whichcomprises a screw on one of said supports, 'a pair of nuts threaded tothe screw, means for maintaining a constant angular relationship betweenthe nuts, and a take-up device having a take-up action to maintain atight operating engagement between said screw and nut elementscomprising tensioning means, take- -up means actuated thereby andcomprising cam 4 actuating surfaces for imparting relative movements tothe nuts cammed at a less than critical locking 'angle to impart anunyielding relative axial movement to the nuts, and means cooperatingwith said take-up device for rigidly positioning said nuts on the otherof said supports against movement relatively thereto with the screw ineither direction, and independent means for moving said take-up meansagainst the pressure of said tensioning means to ease off the take-updevice.

13. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation to anotherwhich comprises a screw on one of said supports, a pair of nuts threadedto the screw, means for maintaining a constant angular relationshipbetween the nuts, a take-up device having a take-up action to maintain atight operating engagement between said screw and nut elementscomprising a rotatable take-up member supported co-axially with thescrew, a spring for rotating said member, cam surfaces renderedoperative by the rotation of said member and cammed at a less thancritical locking angle to exert an unyielding relative take-up strain onthe nuts, and means cooperating with said takeup member for rigidlypositioning said nuts on the other of said supports against movementrelatively thereto with the screw in either direction, and independentmeans for moving the take-up member against the pressure of its springto ease off the take-up device.

14. A mechanism to eliminate backlash between the screw and nut elementsof a driving connection for moving one support with relation to anotherwhich comprises a screw on one of said supports, a pair of nuts threadedto the screw, means for 'maintaining a constant angular relationshipbetween the nuts, a take-up device having a take-up action to maintain atight operating engagement between said screw and nut elementscomprising a take-up nut having

